Mud Volcano

Overview

A quick, high-impact stop, the Mud Volcano Trail is a 0.8‑mile total loop of boardwalks and short paved sections in Hayden Valley. It’s an easy walk with modest elevation (about 100–124 feet of gain) and a whole lot of geothermal drama in a compact package. Expect heat, steam, and a strong sulfur (“rotten egg”) smell—this basin is among the park’s most acidic, where gases interact with groundwater to create bubbling mud and steam vents.

What You’ll See

Right from the trailhead, you’ll encounter classic features like Dragon’s Mouth Spring—a cave-like vent that “breathes” steam and rumbles—and the namesake Mud Volcano and Mud Cauldron. The loop continues past other mudpots, fumaroles, and hot pools, with sections of hillside so thermally active they’re nicknamed for how they “cook” the soil (temperatures around 200 degrees have been noted). Colors skew gray to yellow from sulfur minerals; the sounds and smells are part of the show.

Accessibility & Route Notes

The lower, flatter section between the parking area, Dragon’s Mouth Spring, and Mud Volcano is the most accessible portion, with boardwalk and gentle grades suitable for many wheelchairs, mobility devices, and strollers. The upper loop adds steeper grades (including sections around 8–12%) and stairs; some visitors will need assistance. If you only have a few minutes or want to avoid hills, do the lower boardwalk out-and-back; budget 30–45 minutes for the full loop.

Wildlife

Bison are frequent here and sometimes use the boardwalks. You may also spot elk and mule deer, and in spring, grizzly bears can be in the area. Give all wildlife space—at least 25 yards from large animals—and be ready to wait or turn around if animals block the trail.

Best Time to Hike

Spring through fall is the sweet spot. This is a popular stop on Grand Loop Road, so arrive before 9:00 a.m. or after mid‑afternoon to ease the crowds and parking. Cool mornings keep the steam dramatic for photos, while late-day light and thinning crowds make for a relaxed pass on your way to or from the valley.

Tips & Safety

Stay on marked boardwalks; the ground is thin and features can be near-boiling and highly acidic. The odor is part of the experience—if you’re sensitive, keep your visit brief or stick to the lower loop. Restrooms are at the trailhead (none on the loop). Temporary closures happen due to wildlife or maintenance—have a plan B nearby (Sulphur Caldron is just up the road for a quick peek if this lot is jammed).